Gearless rotary machines operating as positive displacement machines, e.g., either pumps or engines, date back to the early 1900's. For example, U.S. Pat. No. 1,340,625 teaches a rotary machine having a two-lobe lenticular rotor provided with slots which., when the rotor rotates, engage fixed guide members mounted on the machine housing. The slotted rotor construction requires that the machine's rotating shaft be supported completely from one side of the rotor. However, for high speed rotary machines, considerable stresses necessitate that the single shaft support bearing be substantial, i.e., heavy.
In U.S. Pat. No. 4,300,874, a rotary machine includes a slotted rotor for engagement with a large single guide member and a rectangular portion of the shaft that passes therethrough. A first slot accommodates the guide member and a second slot perpendicular to the first slot accommodates the rectangular portion of the shaft. The rotor slidingly contacts the guide member and the rectangular portion of the shaft during eccentric rotation. However, centrifugal forces from the eccentric motion of the rotor are transmitted in alternate fashion between the guide member and the rectangular portion of the shaft thereby causing forces to be concentrated at the various points of contact. This is the source of friction and wear as rotational speed increases.